Re: [boost] Submission: typelist

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-11-28 14:52:56

On Wednesday, November 28, 2001, at 12:32 PM, James S. Adelman wrote:
>
> Nonetheless, two symbols are equal only if one can be used in place of
> another.  This is clearly not the case for int2type, since it maps an 
> int to
> a type, and it is not the case for type2type, since the types are 
> distinct.

wrt int2type, agreed.

You're still not looking at type2type the way I am. Adrei's type2type is 
defined thus:

template <typename T>
struct Type2Type
{
     typedef T OriginalType;
};

If you regard Type2Type as a metafunction, then T is its parameter and 
OriginalType is its return value, in which case it is a true identity 
function.

I realize that that isn't the purpose for which these templates are 
defined in Andrei's code. They really are wrappers, in general used to 
prevent some properties of their parameters from coming into play (e.g. 
a reference type or a compile-time constant integer can be wrapped into 
a value type), so that types and objects can  be treated with more 
uniformity.